Ruthenium metal is excellent in thermal and chemical stability and also has a low resistivity (ρbulk=7.6 μΩ·cm) and a high work function (Fbulk=4.71 eV) and thus can be used as a gate electrode of a transistor or a capacitor electrode material of a DRAM or FeRAM. Particularly, in case of using oxides containing titanium, such as TiO2, STO (SrTiO3), BST [(Ba, Sr)TiO3], and the like, as a source for a high dielectric material of a next-generation DRAM capacitor, it is necessary to use a ruthenium electrode in order to minimize a leakage current.
The ruthenium metal has an excellent adhesion to copper metal and has difficulty in forming a solid solution with Cu, and, thus, application of the ruthenium metal as a seed layer for a Cu wiring process using electroplating in a semiconductor manufacturing process is being actively studied.
Meanwhile, a ruthenium oxide (RuO2) is also a conductive material having a low resistivity (ρbulk=46 μΩ·cm) and an excellent thermal stability even at 800° C. and thus highly likely to be applied as a lower electrode of a metal-insulator-metal (MIM) capacitor in the future.
In order to use the ruthenium metal and the ruthenium oxide as a capacitor electrode of extremely miniaturized next-generation electronic devices, particularly a DRAM (Dynamic Random Access Memory) having a high aspect ratio, it is necessary to apply an organic metal chemical vapor deposition method or an atomic layer deposition method that enables an excellent step coverage on a seriously uneven surface, and, thus, a ruthenium precursor compound suitable therefor is needed.
When a ruthenium metal film or oxide film is formed using the atomic layer deposition method, a bis(ethylcyclopentadienyl)ruthenium [(EtCp)2Ru] precursor compound and an oxygen-containing gas are usually used. However, (EtCp)2Ru is a liquid at room temperature and has a high vapor pressure, but the atomic layer deposition method using the (EtCp)2Ru precursor compound has a problem that particularly initial film growth is very slow. On a silicon oxide film or a silicon nitride film, 100 or more gas supply cycles (incubation cycles) are needed until film growth per gas supply cycle of the atomic layer deposition method can be obtained to a certain degree. The atomic layer deposition method using the (EtCp)2Ru precursor compound also has a defect of slow film growth per source supply cycle (lower than 0.05 nm/cycle) [“Nucleation kinetics of Ru on silicon oxide and silicon nitride surfaces deposited by atomic layer deposition”, Journal of Applied Physics, volume 103, 113509 (2008)].
It has also been known that 2,4-(dimethylpentadienyl)(ethylcyclopentadienyl)Ru (DER) which is a liquid at room temperature and has a relatively high vapor pressure and an oxygen-containing gas are used in the atomic layer deposition method, but it has been reported that in the atomic layer deposition method using the DER, an incubation cycle is needed 100 or 200 times on a titanium oxide (TiO2) or titanium nitride (TiN) substrate, and it has been known that film growth per source supply cycle is only 0.034 nm/cycle [“Investigation on the Growth Initiation of Ru Thin Films by Atomic Layer Deposition”, Chemistry of Materials, volume 22, 2850-2856 (2010)].
Accordingly, a ruthenium precursor compound that enables fast initial film growth during atomic layer deposition or chemical vapor deposition and particularly fast film growth per gas supplying cycle in the atomic layer deposition method.